This proposal is designed to address the possible genetic relationships between the locomotor stimulant effects of ethanol and those of allopregnanolone. We have already analyzed the locomotor stimulant effects of these two compounds in the BXD recombinant inbred mouse set, and identified a statistically significant correlation between the locomotor response to ethanol and locomotor response to allopregnanolone. This analysis has identified a number of provisional quantitative train loci for response to allopregnanolone, some of which are regions known to contain loci for ethanol traits. Here we propose to extend upon these, findings by generating an F2 population which will allow us to confirm or reject these provisional QTLs. Additionally, we will examine locomotor response to allopregnanolone in FAST and SLOW mice selected for their high and low locomotor response to ethanol in order to determine whether selection has favored similar responses to allopregnanolone. We will also determine whether cross sensitization exists between ethanol and allopregnanolone. Finally, we will test finasteride's ability to antagonize the locomotor stimulant effects of ethanol.